Adaptive filtering acquisition method has been proved to be an effective pseudo-noise (PN) code acquisition method in DS-SS system, which is especially useful for long PN code acquisition in low Signal to Noise Ratio (SNR) environment. In order to make use of this method in those PN code acquisition systems with data modulation, a modified adaptive filtering is proposed in this paper, where the effect of polarity reversion caused by data modulation on PN code is removed by employing absolutely successive difference technique in both the received signals and local generated PN code. Compared with the adaptive filtering acquisition method, even with data modulation, the proposed method can attain almost similar acquisition performance, which is tested by simulations.